Nutrient availability and value of poultry litter

Tuesday

Poultry littercan provide a significant and important supply of nutrients for crop productionin areas of Kansaswhere a supply of litter is available. Although Kansasis not a major producer of poultry, there is an abundant supply of litter fromthe nearby states of Arkansas, Missouri, and Oklahoma,which rank among the largest producers of poultry in the U.S.

Theacreage available to receive poultry litter has been declining in Arkansas, Missouri, and Oklahoma in recent yearsbecause of environmental concerns. That trend, coupled with high fertilizerprices, has meant the availability of litter to areas such as southeast Kansas has been on therise.

Poultry littershould serve as an excellent complement to commercial nitrogen (N) fertilizers.Phosphorus content in poultry litter is usually high, and applications ratesshould be based on P levels to avoid potential surface water contamination.

Table 1. Types of Poultry Litter

Source

Typical moisture content

Typical nutrient content (lbs/ton)

N

P

K

Layer

High

35

40

20

Pullet

Low

40

45

40

Breeder

High

40

60

40

Turkey

Low

60

60

55

Broiler

Low

60

60

55

Moisturecontent and nutrient concentration in poultry litter can be highly variable anddepends mainly upon production conditions, storage, and handling methods. Therefore,laboratory analysis is the best way to determine the level of N and P in thematerial to be applied. The table above presents average values for thedifferent types of poultry manure collected over a period of time. The table belowpresents the actual laboratory analysis of 67 poultry manure samples fromsoutheast Kansas.There is a large range in nutrient values, likely due to the source of thelitter. However, a good sample average to expect would be a 55-55-47.

For maximumefficiency of manure use, it is essential to know the nutrient content of themanure. Using a manure lab analysis will help in determining the actualnutrient rates applied. A laboratory analysis should be done on the poultrylitter before applying it to land. A laboratory analyses provides informationregarding nutrient levels, as well as the chemical forms of these nutrients.This information is necessary for an adequate estimation of nutrientavailability and application rates. For more information, see K State Extensionpublication MF-2562, "Estimating Manure Nutrient Availability," at: http://www.ksre.ksu.edu/bookstore/pubs/MF2562.pdf

Nitrogenavailability

Nitrogen andP crop availability shortly after application is a common question. In the caseof N, it is important to consider that this nutrient is primarily in the organicform in poultry litter (up to 75-80% organic). Organic N needs to mineralizebefore becoming available to crops. A fraction of this organic N may becomepart of the soil organic matter pool and unavailable to crops in the short term.

Field andlaboratory studies suggest the fraction of total nitrogen that becomes plantavailable the first year of application is approximately 45-55%, which includesboth the inorganic N in the manure and a percentage of the organic N. Thisvalue varies depending upon components in the litter, and the method ofhandling and application. For example, poultry litter that contains a largefraction of bedding material will tend to have lower N availability the year ofapplication. Reduction in N availability may also occur when litter is aged,and has undergone some level of composting. Nitrogen lost from the volatileammonium fraction at the moment of application to the soil surface can alsoreduce plant available N. Ammonium volatilization is typically higher duringwindy and warm days. Incorporation of litter immediately after application willreduce volatilization and potential loss by water runoff in case of a rainfallevent, in addition to reducing the odor of the litter.

If themanure is applied to pastures, the percentage of nitrogen utilized by theforage the first year will depend on whether the pasture consists ofcool-season or warm-season grasses. For cool-season grasses, such as fescuepasture, nitrogen utilization will likely be less than 50% the first year. Mostof the growth in cool-season pasture occurs early in the year. Microbes willnot mineralize as much N early in the spring as it will later in the summer.Fall applications may utilize more N for fescue than winter or springapplications. For warm-season grasses, such as bermudagrass pasture, nitrogenutilization from manure will likely be close to 50%. In both cases, producersshould base application rates on the P and K needs of the grass, and supplementadditional N fertilizer to meet the N needs of the grass.

Phosphorus and potassium availability

When manureis applied to the soil, what percentage of this phosphorus and potassium isavailable to the crop during the first year?

A largefraction of the phosphorus in manure is considered to be plant availableimmediately after application. The fraction that is not plant available shortlyafter application will become potentially available over time.

Estimatedvalues of phosphorus availability are from 50 to 100%. This range accounts forvariation in sampling and analysis, and for phosphorus requirements withdifferent soil test levels. Use the lower end of the range of phosphorusavailability values (50%) for soils testing "Very Low" and "Low" (below 20 ppm)in phosphorus. In these situations, large yield loss could occur ifinsufficient phosphorus is applied and soil phosphorus buildup is desirable.

On the otherhand use 100% availability when manure is applied to maintain soil testphosphorus in the Optimum soil test category, and when the probability of ayield response is small.

Severalstudies have shown that manure P is a valuable resource, comparable toinorganic fertilizer P for crop production. These two P sources are similarlyeffective when the manure P concentration is known and the manure is appliedproperly.

Nevertheless,excessive application of manure phosphorus (for example, applying manure atrates sufficient to meet the crop's nitrogen needs) often results in excessive soilphosphorus buildup over time, resulting in higher risk of surface watercontamination. This problem of excessive phosphorus buildup in the long-termcan be minimized by:

• Applying manure to cover the phosphorus needs ofthe crop and using inorganic sources of fertilizer to complement nitrogenneeds,

• Constantly monitoring soil test phosphoruslevels, and

• Using the P-index to assess potential impact ofphosphorus buildup on water quality.

Producersshould think in terms of actual phosphorus application rates and not just tonsper acre of manure being applied. Uniform application of manure at preciserates can also be difficult. Careful calibration of manure applicators isneeded. If these aspects are not considered, the efficiency of manure Pcompared with inorganic fertilizer P may be reduced. Careful management paysoff.

Availabilityof potassium (K) is usually near 100% with proper application, poultry littercan also provide significant amounts of secondary and micronutrients.

Value of manure

The use ofpoultry litter can contribute to reduce cost of fertilizer inputs for manyoperations, depending on the price and transportation cost of the litter. Formany farmers the use of poultry litter may represent significant savings.However, for many producers there is a "hassle factor" with using poultrylitter. Reliable delivery, storage sitelocation, uniform application, access to application equipment, and odor canall be additional challenges to producers unfamiliar with its use, and shouldbe a consideration.

How valuable is poultry manure? This may not be astraightforward answer and depends on several factors, including thenutrient(s) required for a specific field, but here's one example using theaverage nutrient analysis values from Labette County of 55-55-47 (N-P-K lbs/ton):